UK What network topology means
Network topology is the arrangement of the devices, called nodes, and the links between them in a network. It describes which device connects to which, and therefore which paths data can take and what happens when a link fails.
There are two views of the same network. The physical topology is how the cables, fibre or radio links actually run. The logical topology is how data flows over them. They often differ: Token Ring was cabled as a physical star to a central wiring concentrator but passed data as a logical ring, and an Ethernet ring is cabled as a loop but runs logically as a line because one link is blocked.
A network topology diagram draws the physical or logical layout, with each switch, router and device as a symbol and each link as a line. It is the first document to reach for when planning an extension or tracing a fault.
Types of network topology
Six layouts cover almost every network, and most real networks combine several of them.
| Topology | How it is connected | Effect of one link failing | Typical use today |
|---|---|---|---|
| Bus | All devices on one shared cable | The segment can fail | CAN, RS-485 and other fieldbuses |
| Ring | Each device to two neighbours in a loop | Reroutes if the ring is protected | Industrial and utility backbones |
| Star | Every device to one central switch | Only that device drops off | Office, home and cabinet LANs |
| Mesh | Devices to several others | Reroutes over another path | Network cores, wireless meshes |
| Tree | Stars joined in a hierarchy | A branch drops off below the fault | Building and campus networks |
| Hybrid | Two or more of the above combined | Depends on where the fault is | Most large networks |
Point-to-point, a single link between two devices, is sometimes listed as a seventh type. It is the building block of the others rather than a layout in its own right.
Physical vs logical topology
The distinction matters most when redundancy is involved. A managed switch network might be cabled as a ring or a mesh for resilience, while the redundancy protocol blocks some links so the logical topology is a loop-free tree. VLANs add another layer: one physical star of switches can carry several separate logical networks, and our explainer on how VLANs split one network into several shows how.
When you document a network, draw both. The physical diagram tells an engineer which cable to check. The logical diagram tells them which way traffic is meant to flow and which links are standby.
Tree and hybrid topologies
A tree topology, also called a hierarchical or extended star topology, joins several stars by linking their central switches to a higher-level switch. Devices connect to access switches, access switches connect to distribution switches, and those connect to a core. The layout scales well and keeps each branch simple, but each uplink is a point of failure for everything below it.
A hybrid topology combines two or more types. A plant might run stars of devices in each cabinet, a fibre ring joining the cabinet switches and a meshed core in the server room. Hybrids are the norm in any network bigger than one room, because each part of the network can use the layout that suits it.
Choosing a topology for an industrial site
Industrial networks follow the shape of the site and the cost of downtime.
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Inside a cabinet: star. The PLC, HMI, drives and edge computer each take a port on a DIN-rail switch, usually unmanaged for a small machine.
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Between cabinets: ring. A ring of managed industrial switches gives every cabinet a second path, with fast recovery when a link fails.
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At the core: mesh or dual links. Core switches are cross-linked, and routing between areas is often done at layer 3. Our guide to when you need a layer 3 switch covers that decision.
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At the machine: bus. Sensors and drives often stay on a fieldbus such as CAN or RS-485, joined to Ethernet by a gateway or computer.
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Out on the line: chain or ring. Roadside, trackside and on-train switches are chained along the route and closed into a ring where redundancy is needed.
Hardware that shapes the topology
The switch is the device that defines most modern topologies, and our explainer on how an Ethernet switch forwards traffic covers the basics. Which switch sits at each point depends on the environment as well as the layout: DIN-rail switches in cabinets, rack mount switches in the server room, and sealed M12 switches on vehicles. Our guide to the types of rugged Ethernet switches compares them.
Before choosing hardware, list what the topology has to deliver: how many devices sit at each location, how far apart the locations are, which devices need power over the cable, and which failures the network must survive without stopping. Those four answers usually settle the layout, the switch type and whether copper or fibre links the locations.
Quick answers on network topology
Network topology: common questions
What is the most common network topology?
The star. Every BASE-T Ethernet network is cabled as a star or extended star around switches, from homes to factories.
What is a home network topology?
Usually a star. Each device connects by cable or Wi-Fi to the home router, which contains a switch and an access point at the centre.
What is a network topology diagram?
A drawing of the network’s layout. It shows each switch, router and device as a symbol and each link as a line, physical, logical or both.
Which topology is the most fault tolerant?
A full mesh. Every node has a direct link to every other, so no single failure isolates anyone. A protected ring is the usual compromise on cost.
Is Wi-Fi a topology?
No, it is a link technology. Wi-Fi devices usually form a logical star around an access point, and mesh Wi-Fi joins access points in a mesh.
We supply industrial, PoE and managed switches with the computers and devices in each system we build, and configure VLANs, redundancy and addressing to fit the topology of your site.